Phil Nelson wrote:
Is there supposed to be a mechanical stop to keep one from turning the
band change dial too far and screwing it up, or from turning it the wrong
way??


I'm not an SX-28 owner or expert but it looks to me like it's a six
position bandswitch with 60 deg indexing. Why would it need a stop?
It seems it would be a lot better to just allow continous rotation
so you wouldnt have to go back through all the positions when going
from a high band to a low band.

73, Roger

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Remember the USS Liberty (AGTR-5)
http://ussliberty.org/

It seems it would be a lot better to just allow continous rotation
so you wouldnt have to go back through all the positions when going
from a high band to a low band.

Yes, on a simpler radio that doesn't have a moving band pilot lamp or shadow
indicator, you certainly could let the bandswitch rotate 360 degrees in
either direction.

This stop is needed because the SX-28 has two string-driven shadow band
indicators, behind the main tuning and bandspread dials, respectively. The
indicators run on little elevators that can go up in one direction, and down
in the other. When an elevator hits the top floor, there's only one
direction to go, and vice versa :-)

The diagram at http://antiqueradio.org/art/temp/SX28DialStringing.jpg
doesn't show all of the parts and pieces, but it does show the strings,
springs, and major doohickeys that make it work. The crossbar carrying the
main tuner shadow indicator is shown where an arrow points to C. The shadow
indicators are simply bent pieces of flat metal with arrow shapes on the
end, which create shadows by sitting between the pilot lamps and the tuning
dials.

Looking at the diagram, find the main tuner bandshaft, where it says
"connected to main tuning knob." If you turn the main tuning knob
counterclockwise, to move you from a lower band to the next higher band,
that will tighten the two sets of strings and lift the two shadow indicators
upward on their elevators. Turn it clockwise, and it will lower the
elevators one floor. But beyond the top and bottom floor, you can't go any
farther without breaking the strings.

Lest you think this is over-complicated, my Midwest DD-18 (
http://antiqueradio.org/MidwestDD-18.htm ) has gizmos that move a pilot lamp
up and down behind a red/green colored screen to illuminate the chosen bands
on the tuning dial. A "Tunalite" circuit is fed off the AVC line and
darkens/brightens the pilot lamp as you tune into a station. A lamp mask on
the bottom half of the dial changes to illuminate the Wavelength markings
accordingly. The good news is that the whole thing is gear-driven -- no
strings to replace!

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

Phil Nelson wrote:


From using my first SX-28, I have to say that the stop feels more
mechanical (i.e., look at your detent assembly), not like hitting the
end of a string. If your bandswitch turns smoothly from one band to
the next, is it possible that somebody disassembled the bandshaft and
left out some pieces, or forgot to tighten things down?

Regards,

Phil Nelson

Phil:
Yeah, it feels like you can turn it past the lower (or upper band) and go
around again and break something. It feels like it's just the cord strength
preventing you from continuing. I don't remember seeing those blocking
washers but I will go inside again and look.

Thanks again Phil, your website has been a huge inspiration and source of
information for work I have done on my 28. Now if I could just get that AVC
working right......

--
Brian Denley
http://home.comcast.net/~b.denley/index.html

In article , "Scott W. Harvey"
writes:

I have seen the "official" tool that was originally used to
attach/remove these rings, and it is a fairly complicated
gizmo....Probably unobtainable unless special-ordered. With that tool,
it's a one-handed job.

If the end tabs of the C-ring each have a hole, then the official tool is
pretty simple. I have a couple of those tools. Unforch, they are "Hong Kong
Hardware" quality tools, and so it's a one-handed job, but very hard on the
throat from the constant profanity needed to "cheer the team" to success.

Maybe you are talking about a larger version of the simple rings, with no tabs,
that hold pot shafts into a pot, for example. Those would require two pliers.
73, Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

In article t, "Phil Nelson"
writes:

This stop is needed because the SX-28 has two string-driven shadow band
indicators, behind the main tuning and bandspread dials, respectively. The
indicators run on little elevators that can go up in one direction, and down
in the other. When an elevator hits the top floor, there's only one
direction to go, and vice versa :-)

The Hammarlund SP-600 has an "elevator" pointer, but it seems to be cam-driven,
so it goes all the way up or donw in a hurry when you roll over the band
selector. Of course, it almost takes two hands to turn the mechanism :-)

BTW, I would want the limit stop detents place up front by the knob, not in the
rear of the bandswitch, so a real gorilla type wouldn't over-torque the switch
shaft.

Just my two cents -- Mike K.



Oscar loves trash, but hates Spam! Delete him to reply to me.